Science Class 8 CBQ of Light Mirrors and Lenses (Critical Clash)

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Science Class 8 CBQ of Light Mirrors and Lenses

Science Class 8 CBQ of Light Mirrors and Lenses

Category 1: Conceptual Understanding

Section A: Multiple Choice Questions (MCQs)

  1. A beam of light striking a reflecting surface at an angle of 900 to the surface itself will experience an angle of reflection equal to:
  1. 900
  2. 450
  3. 00
  4. 1800
  1. In contrast to spherical mirrors, lenses enable us to see objects by looking through them, not by looking into them, due to the following reason:
  1. Lenses reflect all the light that falls onto them.
  2. Lenses are made of transparent materials that permit the transmission of light.
  3. Lenses cause lateral inversion while mirrors do not.
  4. Lenses possess only flat bounding surfaces.
  1. An object is placed extremely close (3–4 cm) to an unknown spherical mirror. The image observed is erect and magnified. When the object is slowly pulled away, the image flips upside down. This mirror is structurally:
  1. Curved outwards like the rear side of a spoon.
  2. Perfectly flat like a standard dressing mirror.
  3. Curved inwards like a dental inspecting mirror.
  4. A combination of an outward and inward bulge.
  1. A spherical mirror is described as having a reflecting surface that curves inwards. Which of the following is true about its schematic representation?
  1. The reflecting surface is shown with shading.
  2. The non-reflecting surface is shown as shaded.
  3. It is consistently depicted as an entirely hollow sphere.
  4. It represents a convex mirror.
  1. What does the normal represent in a reflection diagram?
  1. The incident ray itself
  2. A line at 90° to the mirror at the point of incidence
  3. the reflected ray
  4. The surface of the mirror
  1. A lens thicker at the middle than at the edges is called:
  1. Concave lens
  2. Plane glass
  3. Convex lens
  4. Diverging lens

Science Class 8 CBQ of Light Mirrors and Lenses

Section B: Assertion-Reasoning Questions

Instructions: Choose the correct option:

  1. Both A and R are factually correct, and R provides the precise logical explanation for A.
  2. A is true and R is also true, but R does not logically justify or clarify A.
  3. Assertion A holds true; however, the reason given in R is factually incorrect.
  4. Assertion A is not valid, but the statement in Reason R is accurate.

Assertion (A): When multiple parallel beams of light hit a convex mirror, the reflected rays cross each other at a single real point in front of it.

Reason (R): A convex mirror acts as a diverging system due to the outward bulge of its reflecting surface.

Assertion (A): A plane mirror, a concave mirror, and a convex mirror all exhibit the phenomenon of lateral inversion.

Reason (R): The fundamental laws of reflection are universally valid for all plane and spherical polished surfaces.

Assertion (A): A convex mirror always forms an erect and diminished image.
Reason (R): A convex mirror has a reflective surface that curves outward, which makes the reflected rays spread apart.

Assertion (A): The angle of incidence is always equal to the angle of reflection, regardless of the type of mirror used.
Reason (R): This principle is confirmed by directing a thin ray of light onto a flat mirror and then measuring the angles formed by the rays and the normal line.

Science Class 8 CBQ of Light Mirrors and Lenses

Section C: Short Answer Questions

  1. Explain how spherical mirrors are fundamentally manufactured. Correct the common misconception that they are physically sliced out of a hollow glass sphere.
  2. Contrast a convex lens with a concave lens based purely on their structural thickness profiles from the centre to the margins.
  3. A ray of light is incident on a highly polished flat boundary. If the total angle measured between the incoming incident ray and the outgoing reflected ray is 800, deduce the precise angle of incidence.
  4. State the two laws of reflection. Are they valid for spherical mirrors? Justify.
  5. Why does a concave mirror sometimes produce an inverted image and sometimes an erect image?
  6. What is lateral inversion? Is it seen in spherical mirrors?

Science Class 8 CBQ of Light Mirrors and Lenses

Section D: Long Answer Question

  1. Describe step-by-step how the image characteristics—whether it is real or virtual, upright or inverted, and its size—vary in a concave mirror when the object moves from very close to the mirror to far away.
  2. Describe the reason a small amount of water on an oiled or waxed surface behaves similarly to a magnifying lens. Discuss the roles of surface geometry and transparency in this phenomenon.
  3. Compare the image formed by a plane mirror, concave mirror, and convex mirror when an object is placed very close to them.
  4. Explain the difference between a concave lens and a convex lens in terms of shape and behaviour of light.

Science Class 8 CBQ of Light Mirrors and Lenses

Section E: Case Based Question

  1. Meena is trying to explain to her younger brother how the angle of reflection changes when a light ray hits a plane mirror at different angles. She carefully arranges the setup and takes measurements of the angles. However, her brother accidentally tilts the mirror slightly, but the incident ray still comes in along the normal to the new tilted surface. Meena records her observations in a table.

Table: Measured angles in three cases

CaseIncident ray direction relative to mirror surfaceAngle of incidence (i)Angle of reflection (r)
IAlong the normal to the mirror??
IIMirror tilted; ray still along new normal??
IIIMirror tilted; ray at 20° from new normal??

Which option correctly fills the? in the table?

A) I: i=0°, r=0°; II: i=0°, r=0°; III: i=20°, r=20°
B) I: i=90°, r=90°; II: i=0°, r=0°; III: i=20°, r=40°
C) I: i=0°, r=0°; II: i=90°, r=0°; III: i=20°, r=20°
D) I: i=0°, r=90°; II: i=0°, r=0°; III: i=20°, r=10°

  1. An optics lab technician needs to identify four unlabeled optical components (W, X, Y, and Z) found in a storage cabinet. She places a standard test object exactly 5 cm away from each component and records the orientation and relative size of the resulting image in the table below.
ComponentOrientation of ImageRelative Size of ImageLight Interaction Type
WErectMagnifiedReflects light from its front surface
XErectDiminishedReflects light from its front surface
YErectDiminishedTransmits light through its body
ZErectSame SizeReflects light from its front surface

Question: Based on the image characteristics established in the chapter, which option correctly identifies components W and Y?

(A) Convex lens: W; convex mirror: Y.

(B) Concave mirror: W; concave lens: Y.

(C) W is a concave lens, whereas Y is a convex mirror.

(D) W stands for a convex lens, and Y stands for a convex mirror.

Science Class 8 CBQ of Light Mirrors and Lenses

Category 2: Application

Section A: Multiple Choice Questions (MCQs)

  1. Why do dentists use a small concave mirror instead of a convex one to inspect a patient’s tooth?
  1. It provides a smaller, wider view of the entire mouth.
  2. Placed up close, it provides a virtual, magnified, and erect view of the tooth.
  3. It turns the image of the tooth upside down to check roots properly.
  4. It acts as a transparent window to see inside the gums.
  1. Security personnel at a large apparel department store want to install a single mirror that allows them to scan a vast area of the floor to deter shoplifting. They must choose a:
  1. Concave mirror, because it converges light to a single point.
  2. Plane mirror, because it forms an identical true-to-size image.
  3. Convex mirror, because its outward curve offers a much wider field of view.
  4. Convex lens, because light passes through it to show objects behind.
  1. The metal casing that surrounds a scooter headlight is intentionally made with an inner concave curve. The primary purpose behind this design is to:
  1. Converge diverging light from the bulb into a powerful, focused parallel beam forward.
  2. Scatter light in all directions to illuminate the sky.
  3. Turn the light beam upside down to avoid blinding oncoming traffic.
  4. Diminish the size of the bulb so it consumes less battery power.
  1. Why are side-view mirrors on vehicles convex?
  1. To make objects appear larger
  2. To provide a wider area of the road behind
  3. To invert the image
  4. To reduce glare
  1. A solar concentrator uses mirrors to:
  1. Spread sunlight
  2. Store electricity
  3. Converge sunlight to a small area
  4. Reflect sunlight away
  1. A surveillance mirror in a big store is likely to be:
  1. Concave
  2. Plane
  3. Convex
  4. Opaque

Science Class 8 CBQ of Light Mirrors and Lenses

Section B: Assertion-Reasoning Questions

Instructions: Choose the correct option:

  1. Both A and R are factually correct, and R provides the precise logical explanation for A.
  2. A is true and R is also true, but R does not logically justify or clarify A.
  3. Assertion A holds true; however, the reason given in R is factually incorrect.
  4. Assertion A is not valid, but the statement in Reason R is accurate.

Assertion (A): Side-view mirrors on passenger cars are inscribed with the warning statement: “Objects in mirror are closer than they appear”.

Reason (R): Convex mirrors form diminished images, which tricks the driver’s brain into perceiving the trailing vehicles as being farther away than they actually are.

Assertion (A): High-end astronomical reflecting telescopes use a massive convex mirror as their primary light-gathering component.

Reason (R): Gathering light from distant stars requires a system that converges incoming parallel stellar light beams into a concentrated region.

Assertion (A): Dentists use concave mirrors to examine teeth.

Reason (R): Concave mirrors create an upright and magnified image when placed near the object.

Assertion (A): A magnifying glass is a convex lens.
Reason (R): Water drops on an oily surface act as convex lenses.

Science Class 8 CBQ of Light Mirrors and Lenses

Section C: Short Answer Questions

  1. A person wearing reading glasses notices a distinct, small curved line near the bottom region of their lenses. Speculate on the practical function of this specific design modification.
  2. Imagine three unmarked flat circular discs—one is a plane mirror, one is a concave mirror, and one is a convex mirror. Without touching any of the surfaces, how can you tell which is which?
  3. Explain why convex mirrors are strategically mounted on tall posts at blind, sharp hair-pin bends in mountainous corridors.
  4. Why is the warning “Objects in mirror are closer than they appear” written on vehicle side-view mirrors?
  5. Why are reflectors in torches and car headlights concave?
  6. How does the human eye use a convex lens to see both near and far objects?

Science Class 8 CBQ of Light Mirrors and Lenses

Section D: Long Answer Question

  1. Analyse the technological transition from simple glass windows to specialized optical lenses in modern handheld smartphones. Explain how multiple camera lenses on the back of a phone utilize the properties of light to capture high-clarity photographs.
  2. A modern solar thermal plant utilizes thousands of massive curved reflective arrays to boil a fluid and drive turbines for clean electricity production. Identify the specific type of optical mirror configuration used, explain the physics behind its selection, and map out the energy transformations taking place.
  3. Explain how convex mirrors are used in road safety and surveillance. Give two examples.
  4. Describe the role of lenses in eyeglasses, cameras, and telescopes.

Science Class 8 CBQ of Light Mirrors and Lenses

Section E: Case Based Question

  1. A dentist needs to examine a patient’s molar tooth. She uses a concave mirror to get an enlarged view. She places the mirror very close to the tooth (within 3–4 cm). Then she slowly moves it farther away. She notes the image characteristics in a table.

Table: Image characteristics of concave mirror at different object distances

Distance from object (relative to mirror)Image sizeImage nature
Very close (≈ 2–3 cm)EnlargedErect
Slightly farther (≈ 8–10 cm)EnlargedInverted
Far (≈ 20 cm)DiminishedInverted
Very far (≈ 50 cm)Highly diminishedInverted

Which distance should the dentist use?

  1. Very close (≈ 2–3 cm)
  2. Slightly farther (≈ 8–10 cm)
  3. Far (≈ 20 cm)
  4. Very far (≈ 50 cm)
  1. An engineering firm is designing an automated tracking track for an electric delivery vehicle. The vehicle requires an onboard camera system fitted with a curved mirror to monitor the widest possible area of the road behind it to prevent collisions at blind intersections. The engineers evaluate four mirror samples featuring distinct internal configurations.
PrototypeSurface Curvature Facing TrafficCore Optical Behaviour Observed
1Curved inwards (like the inside of a spoon)Converges incoming parallel beams of light
2Flat and uniformKeeps reflected parallel beams completely parallel
3Curved outwards (like the back of a spoon)Diverges incoming parallel beams of light
4Flat transparent paneTransmits light directly without reflection

To satisfy safety guidelines and match the design of standard vehicle side-view mirrors that provide a wider viewing area, which prototype must the engineering team select?

  1. Prototype 1
  2. Prototype 2
  3. Prototype 3
  4. Prototype 4

Science Class 8 CBQ of Light Mirrors and Lenses

Category 3: Problem Solving & Reasoning

Section A: Multiple Choice Questions (MCQs)

  1. If the angle between an incoming light ray and the surface of a plane mirror is 35°, find the angle at which the ray reflects.
  1. 350
  2. 550
  3. 900
  4. 700
  1. A student moves a toy car away from a convex lens at a constant speed. The student tracks the behaviour of the image viewed through the lens. The image will:
  1. Stay upright and keep growing larger indefinitely.
  2. Flip upside down immediately at any distance.
  3. Remain erect but gradually diminish in size as the distance increases.
  4. Become completely invisible because convex lenses solely reflect light.
  1. Look at the experimental light rays’ diagram below:
CBQ of Light Mirrors and Lenses

If the reflected rays converge together and intersect at a common point, which specific configuration does this system represent?

  1. Parallel beams reflecting from a plane mirror.
  2. Parallel beams diverging from a convex mirror.
  3. Parallel beams converging from a concave mirror.
  4. Parallel beams passing through a concave lens.
  1. A light ray makes an angle of 40° with the normal. What is the angle made by the reflected ray with the mirror surface?
  1. 40°
  2. 50°
  3. 45°
  4. 60°
  1. The mirror is tilted but the light ray still falls along the normal to the tilted surface. What is the angle of reflection?
  1. 0°
  2. 20°
  3. 90°
  4. Cannot be determined
  1. A convex lens is placed such that an object is very far. The image formed will be:
  1. Erect and enlarged
  2. Inverted and diminished
  3. Inverted and same size
  4. No image formed

Science Class 8 CBQ of Light Mirrors and Lenses

Section B: Assertion-Reasoning Questions

Instructions: Choose the correct option:

  1. Both A and R are factually correct, and R provides the precise logical explanation for A.
  2. A is true and R is also true, but R does not logically justify or clarify A.
  3. Assertion A holds true; however, the reason given in R is factually incorrect.
  4. Assertion A is not valid, but the statement in Reason R is accurate.

Assertion (A): If an incident ray strikes a tilted mirror perfectly along its normal vector, the calculated mathematical value for both the angle of incidence i and reflection r is zero.

Reason (R): The normal line by definition forms a 900 angle with the reflecting surface, meaning a ray traveling along the normal has no angular deviation from it.

Assertion (A): A concave lens can be used as a simple burning glass to set a piece of dry scrap paper on fire under bright sunlight.

Reason (R): Concave lenses are diverging lenses that spread light rays over a much larger surface area.

Assertion (A): If the incident ray falls along the normal, the angle of reflection is 0°.
Reason (R): The reflected ray also travels along the normal.

Science Class 8 CBQ of Light Mirrors and Lenses

Section C: Short Answer Questions

  1. A light ray hits a mirror. The angle of incidence is 400. Calculate the exact mathematical value of the angle made by the reflected ray with the mirror’s actual flat surface.
  2. A cap of a sketch pen is placed in front of an unknown mirror. The image seen inside the mirror is upright but significantly smaller than the cap itself. Provide a logical explanation identifying the type of mirror and why it cannot be a plane mirror.
  3. A student views a tall vertical flagpole through a concave lens. Describe what happens to the orientation and size of the flagpole’s image as the student slowly walks backward away from it.
  4. Parallel beams fall on a concave mirror. What happens to the reflected beams and why?
  5. Why does the reflected beam disappear when the paper is bent? Link this concept with the second principle of reflection.
  6. A pencil is placed behind a glass tumbler half-filled with water. Why does it appear bent?

Science Class 8 CBQ of Light Mirrors and Lenses

Section D: Long Answer Question

  1. A laser pointer is aimed at a flat mirror. The mirror is then tilted by an angle of 200 while keeping the incoming laser beam in the exact same position. Trace the path of the normal line and the new reflected ray. Use the laws of reflection to calculate the total angular shift of the reflected ray.
  2. A woman walks toward a large concave mirror in an interactive museum display. She notices that her image starts out upside down and small, grows larger as she walks forward, and then suddenly becomes upright and very large. Explain the underlying physics of this visual transition.
  3. A concave mirror is used by a student to concentrate sunlight onto paper, leading to combustion. Discuss the energy conversion taking place and the reason a convex mirror fails to achieve this.
  1. In both figures show an object O, mirror M, and image I. Figure (a) shows an erect image same size. Figure (b) shows an erect diminished image. Identify the mirror types and justify.
CBQ of Light Mirrors and Lenses
  1. A student measures three pairs: (i=30°, r=29°), (i=45°, r=46°), (i=60°, r=60°). Which pair is most accurate? Explain experimental errors.

Science Class 8 CBQ of Light Mirrors and Lenses

Section E: Case Based Question

  1. A student performs Activity with multiple parallel beams falling on three mirrors: plane, concave, and convex. She records whether reflected beams are parallel, converge, or diverge. Then she calculates the angle between extreme reflected rays for each mirror if the incident beam width is 5 cm and mirror width is 5 cm, assuming focal length of concave mirror = 10 cm and convex mirror = -10 cm.

Table: Behaviour of reflected beams

Mirror typeReflected beam behaviourApproximate angle between extreme reflected rays (calculated)
PlaneParallel0°
ConcaveConverge2 × arctan (2.5/10) ≈ 28°
ConvexDiverge2 × arctan (2.5/10) ≈ 28° (but negative divergence)

Options:

  1. Plane mirror, because reflected rays are perfectly parallel.
  2. Concave mirror, because convergence reduces angle between rays.
  3. Convex mirror, because divergence increases angle.
  4. both concave and convex give the same angle, but plane gives zero.
  1. During a physics practical, a student uses a laser pointer and an adjustable plane mirror platform to verify the laws of reflection. He records his measurements across four experimental runs in the logbook below.
RunAngle of Incidence (i)Angle Between Incident Ray and Tilted Mirror SurfaceTotal Angle Separating Incident and Reflected Rays
A300600600
B450450900
C0090000
D500400800

Question: One of the data entries compiled by the student contains a fundamental error because it directly violates the laws of reflection described in the textbook. Which run contains the invalid dataset?

  1. Run A
  2. Run B
  3. Run C
  4. Run D

Science Class 8 CBQ of Light Mirrors and Lenses

Category 4: Experimentation & Investigation

Section A: Multiple Choice Questions (MCQs)

  1. In a lab activity investigating the laws of reflection, a student uses a black paper strip to mask out all the teeth of a hair comb except for one single slit in the middle. The key purpose behind this step is to:
  1. Block out ambient room light to make the room pitch black.
  2. Isolate a thin, sharp beam of light that can be easily traced on paper.
  3. Remove specific-coloured wavelengths from the torch’s beam.
  4. Increase the total brightness of the light hitting the mirror.
  1. During an outdoor experiment with a concave mirror, a student successfully focuses sunlight onto a piece of newspaper until it begins to smoke and burn. The clear, concentrated bright area appearing on the paper stands for:
  1. A magnified, upright virtual image of the Sun.
  2. A sharply focused, real image of the Sun that is also inverted.
  3. A shadow created by the mirror’s outer frame.
  4. Scattered light reflecting off the grass.
  1. A student places a stiff sheet of chart paper flat on a desk with one section protruding past the table’s boundary. They shine a beam of light across the paper onto a vertical mirror. If they bend the hanging part of the chart paper downward, the reflected light beam traveling across that bent section vanishes. This happens because:
  1. Bending the paper physically blocks the incoming light beam from hitting the mirror.
  2. The reflected ray now travels in a different plane than the bent paper surface.
  3. The mirror’s reflective property is lost once the paper is curved.
  4. Bending the paper changes the chemical properties of the light.
  1. What is the way to differentiate between a concave and a convex mirror by looking at their side profile?
  1. By touching the reflecting surface
  2. By checking if it curves toward the inside or the outside.
  3. By looking at the image size
  4. By measuring weight
  1. Describe the effect of directing parallel beams onto a convex lens.
  1. They pass through unchanged
  2. They converge
  3. They diverge
  4. They are absorbed
  1. Parallel rays of light are directed toward a convex mirror. The reflected beams will:
  1. Remain parallel
  2. Converge
  3. Diverge
  4. Form a real image

Science Class 8 CBQ of Light Mirrors and Lenses

Section B: Assertion-Reasoning Questions

Instructions: Choose the correct option:

  1. Both A and R are factually correct, and R provides the precise logical explanation for A.
  2. A is true and R is also true, but R does not logically justify or clarify A.
  3. Assertion A holds true; however, the reason given in R is factually incorrect.
  4. Assertion A is not valid, but the statement in Reason R is accurate.

Assertion (A): During a lab activity in class where a comb with several slits is used, the rays reflected off a plane mirror stay exactly parallel to one another.

Reason (R): The normal vectors at every single point of incidence on a flat plane mirror point in the exact same direction.

Assertion (A): When a concave lens is used in place of a convex lens in an experiment focusing solar rays, the paper catches fire considerably sooner.

Reason (R): Concave lenses converge all parallel solar rays into a small, hot focal spot.

Assertion (A): When a concave mirror reflects sunlight onto paper, the paper ignites.
Reason (R): Concave mirrors cause parallel light rays to converge at a single focal point.

Science Class 8 CBQ of Light Mirrors and Lenses

Section C: Short Answer Questions

  1. List the safety steps a middle school student should take before working with curved optical devices to focus direct sunlight.
  2. With a drinking glass, a pencil, and water, design a simple experiment that shows light changing direction at the interface between different materials.
  3. A student logs data in a lab table while trying to confirm the first law of reflection, noticing small discrepancies—for example, i = 30° and r = 31.5°. Identify two potential sources of experimental error in a typical classroom setup that could cause these discrepancies.
  4. A student applies a small water drop to a clean glass slide in an attempt to magnify written words, but the drop collapses into a thin, even layer. After rubbing a thin layer of oil or wax on the slide, the same water drop remains rounded and magnifies the text better. What is the reason that oil or wax coating helps maintain the spherical shape of a water drop?
  5. Why should you never look directly at the Sun or at its reflection through a mirror or lens?
  6. If a plane mirror is used instead of the concave mirror, what would the result be? Explain.

Science Class 8 CBQ of Light Mirrors and Lenses

Section D: Long Answer Question

  1. The equipment supplied consists of a flashlight, a comb, a paper clip, black paper, a white sheet of paper, a protractor, a ruler, and a plane mirror. Write a comprehensive laboratory report detailing how to experimentally prove that the angle of incidence equals the angle of reflection. Explain how to set up the experiment, record the data, and take accurate angle readings using a protractor.
  2. Design an investigative experiment to determine which type of lens (convex or concave) is used in a standard magnifying glass. Your plan should list the materials needed, the step-by-step procedure, the observations to look for at different distances, and the criteria for your final conclusion.
  3. Design an experiment using a comb, torch, and three mirrors to demonstrate that concave mirrors converge parallel light. Include steps and expected observation.
  4. A student performs two experiments:

Experiment 1: Observing a toy as it moves from a near position to a far one, first in front of a concave mirror and then in front of a convex mirror.

Experiment 2: Moving the same toy from close to far behind a convex lens and then a concave lens.

Answer the following briefly:

  1. Which mirror and which lens show similar image behaviour (both can give enlarged erect images up close, then inverted images farther away)?
  2. Identify the mirror and the lens that always form erect and diminished images, no matter how far or close the object is placed.
  3. How does the way a concave mirror produces images differ significantly from the way a convex lens does?
  1. Propose an investigation to check if the laws of reflection hold for a concave mirror using a torch, comb, and protractor. Write the steps.

Science Class 8 CBQ of Light Mirrors and Lenses

Section E: Case Based Question

  1. A student replaces the concave mirror with a convex lens to burn paper using sunlight. She holds the lens at different distances from the paper and notes the brightness and size of the spot. She records her findings.

Table: Spot characteristics vs. distance between lens and paper

Distance (cm)Spot sizeBrightnessPaper smoking?
5LargeDimNo
10SmallestVery brightYes, within 30 sec
15MediumMediumNo
20LargeDimNo

Which distance should she use for fastest burning?

  1. 5 cm
  2. 10 cm
  3. 15 cm
  4. 20 cm
  1. Students hide three different transmitting optical elements (lenses or glass plates) inside three separate boxes with slit openings. They project a set of parallel light beams separated by an initial distance of 4 cm into each box and measure the beam spacing as it exits the other side.
BoxSeparation of Light Beams Upon Exiting the BoxSpatial Behaviour of Exiting Light Beams
Box 1Expanded outward to a distance of 8 cmThe beams spread apart (Diverge)
Box 2Remained spaced exactly at 4 cmThe beams stay completely parallel
Box 3Narrowed down to 0 cm at a specific pointThe beams come together (Converge)

Question: By tracking the changing beam width metrics against the standard lens investigations in the textbook, what can the students definitively conclude about the contents of Box 1 and Box 3?

  1. Box 1 contains a convex lens; Box 3 contains a concave lens.
  2. Inside Box 1 is a thin glass plate, and Box 3 holds a concave lens.
  3. Box 1 contains a concave lens; Box 3 contains a convex lens.
  4. Box 1 contains a concave lens; Box 3 contains a thin glass plate.

Category 5: Creativity

Section A: Multiple Choice Questions (MCQs)

  1. Imagine you are designing a stealth spy gadget that lets you look over high walls while remaining completely hidden. Your design uses a long hollow tube. The proper setup requires you to place:
  1. Two concave mirrors at opposite ends facing away from each other.
  2. Two plane mirrors are installed parallel to each other and positioned at 45° angles at the turns.
  3. A concave lens at the bottom and a convex mirror at the top.
  4. A flat piece of window glass at both corners.
  1. You are writing a science fiction story where characters live on an icy planet with no factories. To build a survival tool that can start fires using sunlight, a character should shape a block of clear glacial ice into a:
  1. Thin, flat rectangular sheet.
  2. A lens that is thicker at its center and thinner toward its edges.
  3. Lens that is thin in the middle and thick at the edges.
  4. hollow cylinder open at both ends.
  1. An artist wants to build a “Funhouse Mirror Maze” where visitors look at themselves and see their faces appear giant and stretched out, but their legs look tiny and short. The artist can create this effect by building a single mirror sheet that is:
  1. Perfectly flat from top to bottom.
  2. Concave on the upper half and convex on the lower half.
  3. Convex shape on the upper portion and concave on the lower portion.
  4. Composed of clear window glass treated with an oil layer.
  1. If you had to design a periscope using only spherical mirrors, which combination would give an erect image?
  1. Two concave mirrors
  2. Two convex mirrors
  3. One concave and one convex
  4. Two plane mirrors
  1. Which of the following could be used to create a giant magnifying device without electricity?
  1. Convex mirror
  2. Concave lens
  3. Water-filled large plastic bottle (convex shape)
  4. Plane mirror
  1. To monitor a 360° area in a store with one mirror, you would design a:
  1. Large concave mirror
  2. Dome-shaped convex mirror
  3. Plane mirror system
  4. Parabolic mirror

Section B: Assertion-Reasoning Questions

Instructions: Choose the correct option:

  1. Both A and R are factually correct, and R provides the precise logical explanation for A.
  2. A is true and R is also true, but R does not logically justify or clarify A.
  3. Assertion A holds true; however, the reason given in R is factually incorrect.
  4. Assertion A is not valid, but the statement in Reason R is accurate.

Assertion (A): To design an efficient solar cooker for a school competition, a student should line the cooking box with a highly polished convex mirror.

Reason (R): Convex mirrors scatter light rays outward, spreading solar energy over a very wide area.

Assertion (A): A creative designer can use online simulation tools to model how light rays behave around complex combinations of spherical mirrors and lenses before building a physical prototype.

Reason (R): Virtual simulations accurately use the mathematical laws of reflection and refraction to predict ray paths.

Assertion (A): A solar cooker for a village should use a large concave mirror.
Reason (R): More sunlight concentration means higher temperature.

Section C: Short Answer Questions

  1. Invent a concept for a smart compact makeup or shaving mirror that helps people see fine details on their skin without using any electronic zoom. Explain how the optical components in your product are arranged.
  2. Imagine a world where light travels in curved spiral lines instead of straight lines. Predict how this would change our daily life and how we use standard plane mirrors.
  3. Create a concept for an eco-friendly water droplet microscope using items found around the house. Explain how you would control the shape of the water droplet to change its magnification.
  4. Imagine a mirror that is half concave and half convex. Sketch what an object might look like.
  5. Suggest how convex mirrors could be creatively used on a walking stick to assist someone who is blind.
  6. If you could make a lens from ice, what shape would you use to start a fire? Why?

Section D: Long Answer Question

  1. Write a detailed outline for building a solar cooker at home, designed to heat food using the power of the sun. Your proposal must include:
  • A labelled design sketch.
  • The choice of materials (including the type of mirror or reflective surface used).
  • A detailed explanation of how it uses the properties of light to generate heat.
  • A simple budget and materials list.
  1. Create a script or a detailed storyboard for a 2-minute educational animated video titled “The Great Optical Showdown: Concave vs. Convex”. The characters are a concave mirror/lens and a convex mirror/lens arguing about who is more useful to humans. Write dialogue that highlights their unique characteristics and practical uses.
  2. Design a “solar furnace” for melting small pieces of metal using only concave mirrors and lenses. Draw a labelled diagram and explain the placement.
  3. Your task is to construct a basic projector using a convex lens and a mobile phone. Write the steps and explain how the image will be formed.
  4. Write a short story from the perspective of a light ray entering a concave mirror, then a convex lens, and finally forming a rainbow on a wall.

Section E: Case Based Question

  1. You are designing a solar cooker for your school using the concept from the “Discover, design, and debate” section. You have three reflective surfaces available. Your task is to pick the best option to direct sunlight onto a compact cooking vessel.

Table: Mirror properties

Mirror typeReflectivityShapeEffect on parallel sun raysFocal point temperature estimate
Plane90%FlatReflects without convergingLow
Concave85%InwardConverges to a pointHigh
Convex88%OutwardDivergesVery low
Shiny spoon (concave inner)70%Curved inwardConverges but less preciselyMedium

Which mirror should you choose for fastest cooking?

  1. Plane mirror
  2. Concave mirror
  3. Convex mirror
  4. Shiny spoon (concave inner)
  1. An amateur filmmaker wants to construct a simple DIY projector attachment for his phone to display small typography onto a nearby wall. The text must look upright (erect) and enlarged when placed close to the lens module. He writes down four different substances and shape designs as possible options for building the lens frame of his prototype.
Concept DesignBase Material ChoiceGeometry profileLight Transmission Class
Concept KOpaque Polished MetalCurved neatly inward like a small dishReflective
Concept LTransparent Clear GlassThicker at the middle than at the edgesTransmissive
Concept MTransparent Clear PlasticThicker at the edges than at the middleTransmissive
Concept NSemi-opaque Frosted GlassFlat, texturized uniform paneDiffusive

Question: The filmmaker needs a working prototype that functions like an ordinary magnifying glass—magnifying text sharply and transmitting light straight from the phone screen. Which design route should be selected?

  1. Concept K
  2. Concept L
  3. Concept M
  4. Concept N

Category 6: Values & Awareness

Section A: Multiple Choice Questions (MCQs)

  1. Promoting the use of solar concentrators and solar cookers in rural communities is an excellent way to support environmental sustainability because it:
  1. Increases our reliance on imported fossil fuels.
  2. Reduces wood cutting, lowers carbon emissions, and saves electricity.
  3. Changes the global path of sunlight.
  4. Eliminates the need for clean drinking water.
  1. Why is it crucial to learn about the correct types of lenses used in eyeglasses?
  1. It helps us choose stylish frames for fashion trends.
  2. It helps us understand how optical technology corrects vision issues, improving our quality of life.
  3. It allows us to see through solid walls.
  4. It shows us how to block all light from entering our eyes.
  1. Which safety rule is most important to follow when working with optical devices like magnifying glasses or concave mirrors outdoors?
  1. Always wear heavy insulated gloves.
  2. Never look directly at the Sun or point concentrated sunlight at anyone’s eyes.
  3. Clean the mirror surface with oil before going outside.
  4. Keep the mirror moving quickly so it stays cool.
  1. Why should you never look directly at the Sun through a convex lens?
  1. It will hurt your eyes due to concentrated light
  2. The lens will melt
  3. You will see an inverted image
  4. it is illegal
  1. Using solar concentrators for melting steel is:
  1. Dangerous and should be banned
  2. An eco-friendly method
  3. Impossible
  4. Only for small-scale cooking
  1. What safety awareness does the warning ‘Objects in mirror are closer than they appear’ help to foster?
  1. Fear of mirrors
  2. Driver awareness and safety
  3. Mirror manufacturing standards
  4. None of the above

Section B: Assertion-Reasoning Questions

Instructions: Choose the correct option:

  1. Both A and R are factually correct, and R provides the precise logical explanation for A.
  2. A is true and R is also true, but R does not logically justify or clarify A.
  3. Assertion A holds true; however, the reason given in R is factually incorrect.
  4. Assertion A is not valid, but the statement in Reason R is accurate.

Assertion (A): Studying past scientific milestones—such as the way astronomers employed water reflections to observe planets eight centuries ago—deepens our respect for our scientific legacy.

Reason (R): Historical optical tools show that ancient cultures understood and applied the practical principles of light long before modern textbooks were written.

Assertion (A): Public vehicles must maintain clean, undamaged side-view convex mirrors to ensure road safety.

Reason (R): By offering a wider field of vision to the rear, side mirrors assist drivers in avoiding accidents when shifting lanes

  1. Assertion (A): Solar cookers help save electricity and reduce fossil fuel use.
    Reason (R): Mirrors serve to direct and intensify sunlight.

Section C: Short Answer Questions

  1. Explain how assistive optical technologies, like specialized lenses and eyeglasses, help create an inclusive environment for individuals with vision challenges.
  2. Provide a concrete example of how virtual lab simulations can enhance science learning for students attending schools that lack costly physical apparatus.
  3. Discuss how ancient Indian astronomers, during the time of Bhāskara II, used shallow bowls of water and tubes to measure the positions of stars. What insight does this provide into their real-world understanding of light?
  4. A student focuses sunlight onto a sheet of paper using a concave mirror. What two important safety measures should the student follow during this activity?
  5. Explain the importance of supervising children when they work with concave mirrors and sunlight in experiments.
  6. What role can understand spherical mirrors play in enhancing road safety and reducing crashes?

Section D: Long Answer Question

  1. Talk about how scaling up solar furnace technology (using huge concave mirror systems to melt steel) might affect communities and the environment, compared to traditional blast furnaces that run on coal. Consider energy savings, minimizing pollution, and the difficulties posed by depending on weather patterns.
  2. Think about what it means to ‘stay curious.’ Write an essay explaining how asking questions about ordinary things—such as labels on car mirrors or the curved design of eyeglasses—fuels scientific discovery and progress in technology for communities.
  3. The PDF notes that astronomers during the time of Bhaskara II used shallow water-filled bowls to observe stars. What does this reveal about India’s historical contributions to science? What values does it teach?
  4. Write a dialogue between two students: one arguing for using convex mirrors on all school bus mirrors, the other arguing for plane mirrors. Which one wins and why?
  5. Prepare an itemized budget for implementing a solar cooker project at school, utilizing concave mirrors as the primary component. Include details on materials, safety measures, and community benefits, referencing the ‘Discover, Design, and Debate’ segment.

Section E: Case Based Question

  1. A village in Rajasthan uses a solar furnace based on a large concave mirror to melt steel for making small tools. The mirror concentrates sunlight to generate extreme heat. However, some villagers suggest replacing it with a convex mirror because it’s cheaper and gives a wider view.

Table: Comparison of mirrors for solar furnace

Mirror typeHeat concentrationUse in solar furnaceWider view for traffic?Cost
ConcaveYes (high)SuitableNoHigh
ConvexNo (diverges)UnsuitableYesLow
PlaneNoUnsuitableNoLow
Shiny metal sheet (flat)NoUnsuitableNoLow

Which statement is correct?

  1. Use convex mirror — it gives wider view and is cheaper, good for safety.
  2. Use concave mirror — only it can concentrate sunlight enough to melt steel.
  3. Use plane mirror — it’s simplest and reflects all light.
  4. Use convex mirror — it can also converge light if made larger.
  1. A rural cooperative is looking to set up an off-grid solar-powered community kitchen. They are testing three styles of large mirror configurations to determine which system can safely and effectively bundle raw sunlight onto a cookpot to generate enough localized thermal energy to boil water.
Solar RigReflective Assembly ShapeObservable Heat Concentration Potential
Rig AlphaFormed entirely of flat plane mirror panelsSpreads solar rays over an area equal to the mirror size; no focal point.
Rig BetaFormed of a uniform spherical surface curved inwardCollects a wide area of sunbeams and concentrates them into a single sharp spot.
Rig GammaFormed of a spherical surface bulging outwardBounces incoming sunbeams widely away in all directions away from the pot.

Question: Based on environmental awareness and the textbook’s details regarding solar concentrators, which rig setup should the community deploy to successfully ignite fuel or heat liquid?

  1. Rig Alpha is preferable because flat plane arrays are easier to maintain and clean.
  2. Rig Beta, because it concentrates light after reflection onto a single point, generating sufficient heat.
  3. Rig Gamma, because diverging solar rays provides uniform heating across the entire bottom of the kitchen floor.
  4. Any of the three rigs, as long as they are placed directly under open sunlight.

Answer Key & Reference Guide

Category 1: Conceptual Understanding

Section A: Multiple Choice Questions (MCQs)

Q. No.AnswerExplanation
1CIf the beam strikes the surface at 90° to the surface, it is actually along the normal. When the angle of incidence is 0°, the angle of reflection is also 0°.
2BLenses work by refraction (transmission), not reflection.
3CA concave mirror produces erect, magnified image when object is very close (within focus), and inverted beyond focus.
4BIn diagrams, the non-reflecting (back) side of a concave mirror is shaded.
5BThe normal is perpendicular to the surface at the point of incidence.
6CA convex lens has a thicker center compared to its edges.

Section B: Assertion-Reasoning Questions

Q. No.AnswerExplanation
7dConvex mirrors diverge rays (R correct), but parallel rays do not meet at a real point in front — they appear to diverge from a virtual focus behind.
8bAll mirrors do show lateral inversion, and laws of reflection are universal, but lateral inversion is a consequence of geometry, not directly the laws.
9aDiverging rays produce erect, diminished virtual images regardless of object distance.
10aThe law is true for all mirrors, but citing one activity doesn’t prove universality — it’s just an observation.

Section C: Short Answer Questions

Q. No.Answer Key Points
11Spherical mirrors are made by silvering one surface of a curved glass piece, not by slicing a hollow sphere. The glass is first shaped, then coated.
12Convex lens: thicker at center, thinner at edges. Concave lenses have a thinner central portion and thicker outer edges.
13If total angle between incident and reflected rays is 80°, then angle of incidence = 40° (since i = r, and i + r = 80° → 2i = 80° → i = 40°).
14The incident ray, the reflected ray, and the normal all lie in the same plane.For a spherical mirror, the angle of incidence is equal to the angle of reflection at every point along its surface.
15Inverted when object is beyond focus (real image); erect when object is between pole and focus (virtual image).
16Left-right reversal in image. Yes — seen in all mirrors (plane and spherical).

Section D: Long Answer Questions

Q. No.Answer Key Points
17Very close: erect, magnified, virtual. At focus: no image. Between F and C: inverted, magnified, real. At C: same size, inverted, real. Beyond C: inverted, diminished, real. When an object is placed far away from a spherical mirror, the image formed is real, inverted, highly diminished in size, and located at the focal point.
18Drop is convex in shape (bulging) → acts as convex lens. Transparency allows light transmission. Surface tension creates spherical curvature.
19Plane mirror: same size, erect, virtual. Concave (very close): magnified, erect, virtual. Convex (very close): diminished, erect, virtual.
20Concave: diverges light, thinner middle. Convex: converges light, thicker middle.

Section E: Case Based Question

Q. No.AnswerExplanation
21AAlong normal → i=0°, r=0° always. For tilted mirror but ray along new normal → still 0°. If a ray strikes a surface making a 20° angle relative to the new normal, then both the angle of incidence and the angle of reflection are 20°.
22BConcave mirror (close object) → erect, magnified. Concave lens → always erect, diminished, virtual (transmits light).

Category 2: Application

Section A: Multiple Choice Questions (MCQs)

Q. No.AnswerExplanation
1BConcave mirror, when object is between pole and focus, gives erect, magnified, virtual image — useful for detailed dental exam.
2CConvex mirrors diverge rays, covering a larger area than plane or concave mirrors.
3AA concave reflector placed behind a bulb collects the outgoing light and reshapes it into a parallel beam, allowing for effective forward illumination.
4BConvex mirrors give a wider field of view, reducing blind spots.
5CSolar concentrators use concave mirrors to focus sunlight for heating or power generation.
6CSurveillance mirrors in stores are convex to cover a wide area.

Section B: Assertion-Reasoning Questions

Q. No.AnswerExplanation
7ADiminished image → perceived distance is greater than actual → closer than they appear warning.
8DR is true (convergence needed), but telescopes use concave (not convex) primary mirrors to converge light.
9AA concave mirror produces an enlarged and upright image when the object is placed close to the focus, making it well-suited for dental examinations.
10BBoth are true, but water drop example doesn’t explain why magnifying glass is convex lens — different contexts.

Section C: Short Answer Questions

Q. No.Answer Key Points
11The small curved line is likely a bifocal segment — for near vision (reading) vs. distance vision.
12Look at the reflection of your face: same size → plane; enlarged → concave; diminished → convex. No touching needed.
13Convex mirrors give drivers a wider field of view, making it easier to spot oncoming vehicles around blind curves.
14Convex mirrors make objects appear smaller and farther; the warning corrects this misperception.
15The goal is to channel the light produced by the bulb into a beam that is either parallel or concentrated, thereby enhancing the illumination quality.
16Eye lens changes shape (accommodation) — flatter for distant objects, rounder for near objects — focusing light onto retina.

Section D: Long Answer Questions

Q. No.Answer Key Points
17From single glass (basic refraction) to multi-lens systems (wide, telephoto, macro). To obtain sharp, high-resolution images, optical systems rely on refraction, precise focusing, and the correction of aberrations.
18Concave mirrors (parabolic) — focus sunlight on receiver. Solar energy is converted into thermal energy, which then becomes mechanical energy to drive a turbine, and finally that mechanical energy is transformed into electrical energy.
19(1) Road safety mirrors at blind turns. (2) Store surveillance mirrors. Both provide wide-angle view.
20Eyeglasses: correct focus on retina. Cameras: focus light on sensor. Telescopes: gather and magnify distant light using lenses/mirrors.

Section E: Case Based Questions

Q. No.AnswerExplanation
21AAn enlarged and upright image is achieved only when the object is positioned between the pole and the focus, meaning it must be placed very close to the mirror.
22CWhen a mirror bulges outward, it is called a convex mirror. This shape makes light rays spread apart, giving a wider viewing area. This is why convex mirrors are commonly used as side mirrors on vehicles.

Category 3: Problem Solving & Reasoning

Section A: Multiple Choice Questions

Q. No.AnswerExplanation
1BIf a ray hits a surface at 35° measured from the surface itself, then its angle relative to the normal is 55° (since the normal is perpendicular to the surface, so 90° – 35° = 55°). The law of reflection tells us that the angle of reflection must be the same as the angle of incidence, so it is also 55°.
2CWhen an object is placed closer to a convex lens than the focal point, the image appears upright and enlarged. As the object moves farther away, the image remains upright but becomes smaller, until it passes the focal point.
3CConcave mirrors converge parallel incident rays to a real focus.
4BAngle with normal = 40 degree (incidence). The reflected ray also forms a 40 degree angle with the normal, which means it makes a 50 degree angle with the mirror surface (since 90° – 40° = 50°).
5AWhen a ray travels along the normal to any surface, both the angle of incidence and the angle of reflection are zero degrees.
6BFor an object situated at a great distance, the image is formed at the focal point, and it is real, inverted, and extremely small.

Section B: Assertion-Reasoning Questions

Q. No.AnswerExplanation
7AIf a ray strikes a surface along the normal, then the angle of incidence is zero, and consequently, the angle of reflection is also zero. R correctly defines normal.
8DThe statement of reason (R) is accurate, as concave lenses cause light rays to diverge. But the assertion (A) is wrong because a concave lens is unable to set paper on fire—only a convex lens is capable of focusing sunlight to a point.
9AWhen light strikes a surface at normal incidence, the angle of incidence is 0°, so the reflected ray also travels back along the normal, making the angle of reflection 0° as well.

Section C: Short Answer Questions

Q. No.Answer Key Points
10If the angle of incidence is 40°, then the angle of reflection is also 40° measured from the normal. Relative to the mirror surface, this angle equals 50° (because 90° minus 40° equals 50°).
11A convex mirror consistently produces an erect and diminished image. A plane mirror is incapable of this, since it consistently produces an image that matches the object’s size.
12Concave lens always gives erect, diminished, virtual image. A plane mirror cannot achieve this because the image it forms is always identical in size to the object.
13Reflected beams converge to a point (focus). Reason: Concave mirror converges parallel rays.
14If you bend a piece of paper, the surface where light strikes becomes irregular. Because of this, the normals at different points no longer point in the same direction. As a result, the normals at various points no longer align in the same direction. This breaks the rule that the incoming ray, the outgoing ray, and the normal must all stay within one plane.
15Due to refraction of light at water-air interface (different optical densities) — pencil appears bent.

Section D: Long Answer Questions

Q. No.Answer Key Points
16When the normal rotates by 20°, and the incident ray stays unchanged, the new angle of incidence becomes 20°. Based on the law of reflection, the updated angle of reflection measures 20°. Total angular shift of reflected ray = 40°.
17If you position an object beyond the focal length, the image formed will be upside down, reduced in size, and capable of being projected on a screen (real). When an object is positioned between the focal point and the pole of a mirror, the resulting image is magnified, upright, and virtual. Transition happens at focal point.
18When sunlight strikes a concave mirror, the mirror brings all the rays together at its focal point. The concentrated heat at that spot is strong enough to ignite paper. In contrast, a convex mirror spreads light rays apart, so it cannot concentrate heat at any single point.
19Figure (a): Plane mirror (erect, same size). Figure (b): Convex mirror (erect, diminished).
20Among all the angle pairs recorded, the one with both angles equal to 60° is the most accurate. The other pairs are less reliable. For example, the readings (30°, 29°) are likely off because of parallax or a mistake in reading the protractor. The pair (45°, 46%) suggests some kind of error — either systematic or random in nature.

Section E: Case Based Questions

Q. No.AnswerExplanation
21AOn a plane surface, the reflected rays remain parallel to each other, resulting in an angle of 0° between them — the smallest possible angle. Both concave and convex mirrors produce an approximate divergence or convergence angle of 28°.
22DThe total angle between the incident ray and the reflected ray is equal to i + r. Since the angle of incidence equals the angle of reflection (i = r), this sum is simply 2i. In Run D, the angle of incidence is 50 degree, so the total angle between the incident and reflected rays should be 100 degree (since 2i = 100°). Nevertheless, the measured value of 80 degree does not comply with the law of reflection.

Category 4: Experimentation & Investigation

Section A: Multiple Choice Questions

Q. No.AnswerExplanation
1BA single slit produces a narrow, well-defined ray for accurate tracing.
2BConcave mirror forms real, inverted, diminished image of Sun at focus; concentrated heat burns paper.
3BLaws of reflection require incident and reflected rays to be in same plane; bending paper moves it out of that plane.
4BConcave curves inward (like a cave); convex curves outward.
5BParallel light rays are brought together at a single focal point by a convex lens.
6CConvex mirror diverges parallel incident rays.

Section B: Assertion-Reasoning Questions

Q. No.AnswerExplanation
7AParallel incident rays on plane mirror → parallel reflected rays because normals are all parallel.
8DR is false (concave lenses diverge, not converge). A is also false (concave lens won’t burn paper).
9AConcave mirror converges sunlight to focus → sufficient heat to ignite paper.

Section C: Short Answer Questions

Q. No.Answer Key Points
101) Wear safety goggles. 2) Never look directly at Sun. 3) Use dark paper, not flammable surface nearby. 4) Keep fire extinguisher/water nearby. 5) Perform in shade or controlled light.
11Fill tumbler ¾ with water. Insert pencil partially. Observe from side → pencil appears bent at water-air interface due to refraction.
121) Parallax error while reading protractor. 2) Inaccurate alignment of comb slit with mirror. 3) Paper not perfectly flat. 4) Thickness of traced lines.
13Oil or wax makes the glass surface hydrophobic (water-repelling), preventing water from spreading. This forces the water drop to maintain a curved, dome-like shape, which acts like a convex lens to magnify the text.
14Concave mirrors and convex lenses concentrate sunlight into a small, intense spot. Looking directly at the Sun or its reflected rays can cause permanent eye damage or blindness because the concentrated light burns the retina.
15Plane mirror reflects parallel rays as parallel → no convergence → no bright hot spot → paper won’t burn.

Section D: Long Answer Questions

Q. No.Answer Key Points
16Setup: White sheet on board, mirror along line, comb + torch to produce single ray. Steps: Trace incident/reflected rays, draw normal, measure i and r with protractor. Repeat for different angles. Conclude i = r.
17Materials: Unknown lens, paper, ruler, window/sunlight. Procedure: Hold lens over paper in sunlight. If it converges to bright small spot → convex (magnifying glass). If it diverges → concave. Also test near objects: erect magnified = convex.
18Materials: Torch, comb, concave mirror. Steps: Produce parallel rays using comb. Direct at concave mirror. Observe reflected rays meet at a point (focus). Conclude convergence.
19Concave mirror and convex lens.Convex mirror and concave lens.Concave mirror reflects light; convex lens refracts light. Also, concave mirror can form real images on a screen, while convex lens forms real images on the opposite side.
20Steps: Mount concave mirror on sheet. Use comb + torch to get parallel rays hitting mirror at different points. Trace incident & reflected rays, draw normals (radial lines from center of curvature). Measure i and r for each ray. Verify i = r.

Section E: Case Based Questions

Q. No.AnswerExplanation
21bSmallest spot size + brightest + paper smokes → represents focal point where rays converge maximally.
22cBox 1: beams diverge → concave lens. Box 2: parallel → glass slab. Box 3: converge to point → convex lens.

Category 5: Creativity

Section A: Multiple Choice Questions

Q. No.AnswerExplanation
1BThis describes a periscope — allows seeing over obstacles while remaining hidden.
2BConvex lens (ice can be shaped into one) converges sunlight to start a fire.
3CConvex makes face look smaller/stretched; concave makes legs look larger/short — creative distortion.
4ATwo concave mirrors placed appropriately can produce an erect image in a periscope-like design (though plane mirrors are standard).
5CWater + transparent convex shape acts as a large magnifying lens without electricity.
6BA dome (spherical convex) provides 360° wide-angle surveillance.

Section B: Assertion-Reasoning Questions

Q. No.AnswerExplanation
7DR is true (convex mirrors diverge light), but A is false — convex mirror is poor for solar cooker; concave mirror is correct.
8ASimulations rely on optical laws to accurately model ray behavior before physical prototyping.
9AConcave mirror converges sunlight to focus → high heat → efficient cooking.

Section C: Short Answer Questions

Q. No.Answer Key Points
10Compact concave mirror with adjustable distance from face. Concave mirror, when held close, gives erect, magnified image — ideal for detailed skin/facial hair viewing.
11Plane mirrors would not form predictable images. Reflection angles would spiral, making self-image distorted. Navigation, periscopes, telescopes would fail. Basic optics would need complete redefinition.
12Use a glass slide or plastic sheet with a tiny hole. Place water drop over hole. To change magnification: add/remove water (changes curvature). Use syringe for precise control.
13Object would appear: upper part (concave) — enlarged/inverted; lower part (convex) — diminished/erect. Funny, distorted composite image.
14Convex mirror on stick end — provides wide field of view ahead/around obstacles; alerts blind person to approaching people/vehicles via auditory feedback (paired with sensor).
15Convex shape (thick center, thin edges). Because convex lens converges parallel sunlight to a hot focus point — can ignite tinder.

Section D: Long Answer Questions

Q. No.Answer Key Points
16Sketch: Box with concave mirror lining, black pot at focus. Materials: cardboard box, aluminium foil (concave curved surface), glass cover, black paint. Light converges → heat. Budget: low-cost (<₹200).
17Script: Concave: “I magnify teeth for dentists!” Convex: “I see around blind corners!” Concave lens: “I fix near-sightedness!” Ending: “Together we serve humanity.”
18Diagram: Primary concave mirror collects sunlight → reflects to secondary convex/concave mirror → converges to small metal crucible. Multiple mirrors in array for higher temperature.
19Steps: 1) Dark room. 2) Place phone (brightness max) facing wall. 3) Convex lens between phone and wall. 4) Adjust distance until sharp inverted image forms. Use inverted display app to get erect final image.
20Story: “I am Ray. Concave mirror aimed me at focus. Convex lens bent me further. Then prism split me into rainbow — painting colours on wall. What a journey!”

Section E: Case Based Questions

Q. No.AnswerExplanation
21BBest combination of high reflectivity (85%) and converging shape → highest focal temperature.
22BTransparent + thicker in middle = convex lens → transmits light and magnifies (like magnifying glass).

Category 6: Values & Awareness

Section A: Multiple Choice Questions

Q. No.AnswerExplanation
1bSolar cookers use renewable energy, reducing deforestation and fossil fuel dependence.
2bKnowledge of lenses enables corrective eyewear, enhancing vision and daily functioning.
3bConcentrated sunlight can cause permanent eye damage or blindness.
4aConvex lens focuses sunlight onto retina → severe burns.
5bSolar melting uses renewable energy, no fossil fuels or CO₂ emissions.
6bWarning corrects distance misperception, preventing collisions.

Section B: Assertion-Reasoning Questions

Q. No.AnswerExplanation
7aHistorical optical innovations demonstrate ancient practical knowledge, enriching our scientific heritage.
8aClean convex mirrors provide wider view → safer driving → justifies maintenance need.
9bBoth true, but saving electricity/fuel is a broader environmental benefit; concentration is just the mechanism.

Section C: Short Answer Questions

Q. No.Answer Key Points
10Corrective lenses (concave for myopia, convex for hyperopia) restore clear vision. This enables education, employment, and independent living → inclusivity.
11Example: Students without concave mirrors can simulate ray convergence on free software (e.g., PhET). Low-cost, accessible, repeatable.
12Water bowls acted as primitive reflecting surfaces (mirrors). Shows they understood reflection, angles, and celestial tracking without modern tools.
131) Never look at Sun directly. 2) Use dark paper, not flammable cloth. 3) Perform in shade. 4) Have water nearby. 5) Wear sunglasses.
14Children may accidentally look at Sun or ignite nearby objects. Supervision ensures safe handling and immediate response to fire risk.
15Convex mirrors on blind turns/vehicles reduce blind spots → fewer collisions. Concave mirrors in headlights focus beams for better night vision.

Section D: Long Answer Questions

Q. No.Answer Key Points
16Environmental: No CO₂, no mining pollution. Social: Jobs in rural areas, lower energy costs. Challenges: Weather-dependent, night operation impossible, high initial cost.
17Curiosity leads to questions → experiments → discoveries. Example: Car mirror warning led to understanding convex mirror distortion. Drives lenses, telescopes, medical imaging.
18India had advanced astronomy/optics centuries ago. Teaches: Observation, documentation, practical application, and respect for indigenous knowledge systems.
19Student A (convex): Wider view, fewer blind spots, safer for children. Student B (plane): True size/distance. Winner: Convex — safety outweighs distortion with warning label.
20Materials: Concave mirror (₹500), metal stand, black pot, glass lid. Total ~₹800. Safety: Goggles, supervision. Benefits: No fuel cost, smoke-free, empowers women.

Section E: Case Based Questions

Q. No.AnswerExplanation
21bConvex diverges; plane reflects without focusing. Science + sustainability demand concave.
22bInward-curved (concave) spherical surface → convergence → high temperature for cooking.

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